Process of impregnating porous material with solid substances



Patented Feb. 6, 1934 UNITED STATES PROCESS OF IMPREGNATING POROUS MA- TERIAL WITH SOLID SUBSTANCES Alexander Winogradow, New York, N. Y.

No Drawing. Application July 22, 1930 Serial No. 469,939

9 Claims.

This invention relates to the fireproofing of fibre board having the characteristics of such products bearing the trade names of Celotex,

Nu-wood, Maftex, Vazcane, and insulating board.

These contain wood fibre obtained from various sources such as wood pulp, the fibres of the roots of licorice and sugar cane. This type of board is light and porous, elastic and readily compressible. It is a property of this material even though porous, that it is not readily wet by water. This material is fireproof by depositing in it a fireproofing salt. The minimum amount of such salt, necessary to effect the fireproofing, Per unit of the material is well known to the art and can be readily determined for a particular case. The invention consists essentially in causing a solution of the salt containing a higher concentration of the fireproofing salt than necessary for fireproofing to impregnate the fibre board, and then to squeeze out enough of the solution from the board, so that the salt in the solution remaining in the board, is sufficient to effect the fire-- proofing of the board. After the squeezing the board is dried. 25 It is one of the advantages of my process that the salt is uniformly distributed throughout the mass of the material. Attempts heretofore made with fibre board by causing a water solution of the salt to impregnate the material and then letting it dry, without squeezing, give poor results as the salt does not crystallize out uniformly through the material, and a heavy crust of the salt usually is formed on the surface.

The squeezing as used in my process also facilitates the drying of the board through the creation of air spaces. It decreases the amount of water to be evaporated and substantially reduces the tendency for the formation of a crust of the salt on the surface, and causes a more complete distribution of the salt in the board than otherwise. The squeezing breaks up the continuity of the solution throughout the mass by forming air pockets, tending to isolateone portion of the solution from another and thus prevent a fiow of the salt, as the solution evaporates, from one portion of the mass to another and to the surface.

The amount of the pressureused in squeezing should be such that the board is not crushed and its characteristics impaired. It should be within the elastic limit of the material, that is such a limit with this material; that said material will recover substantially its original volume in a reasonable time.

Owing to the fact that it is difficult to wet fibre board, it is preferred to force the solution into the board under pressure or by means of vacuum. The forcing of solution into a fibrous substance by means of a vacuum step is well known to the art, and consists in subjecting the solution with the substance in it to a vacuum. This removes the air from within the substance, and then when the vacuum is taken off, the solution is forced into the substance by the atmospheric pressure.

The pressure and length of time during which the board immersed is just suflicient to impregnate it, that is just enough so that the solution only occupies the spaces between the fibres and does not enter the fibres themselves. Too great a pressure and too long an immersion would tend to impair the original properties of the material, such as its water repellant property.

Some of the salts suitable for my process are:

(NH4) 2SO4 ammonium sulphate NH4H2PO4 mono-ammonium phosphate (NH4)2HPO4 di-ammonium phosphate Na2WO4.2H2O sodium tungstate.

As a particular example of my process, three pounds of a 25% solution of mono-ammonium phosphate in water are forced under pressure into a one pound board of Celotex, about one half inch thick. It is then squeezed by rolls or by plates up to substantially its elastic limit, removing thereby a considerable amount of the solution. The board is then left to dry.

I claim:

1. The process of fireproofing fibre board consisting in impregnating said board by immersing it in a solution of a fireproofing salt and then subjecting said solution to a pressure other than atmospheric, then squeezing said board after being removed from the solution with sufficient pressure to reduce its volume enough to effect the removal from within the board of enough solution .to effect the formation of air pockets 'in the board, and then drying the board. 2. The process of impregnating resilient fibre board of substantial thickness, with a salt, consisting in completely impregnating said board with a solution of a salt, removing from throughout the thickness of said board a portion of said solution by squeezing the board up to substantially its elastic limit and then effecting the drying of the board;

3. The process of fireproofing fibre board consisting in immersing said board in a solution of 106 mono-ammonium phosphate, subjecting said solution with the board in it to a pressure other than atmospheric, then squeezing said board after being removed from the solution, with 'sufficient pressure to reduce its volume enough to effect 110 the removal from within the board of enough solution to effect the formation of a substantial amount of air pockets in the board, and then drying the board.

4. The process of fireproofing fibre board consisting in immersing said board in a solution of ammonium sulphate, subjecting said solution with the board in it to a pressure other than atmospheric, then squeezing said board, after being removed from the solution, with sufficient pressure to reduce its volume enough to effect the removal from within the board of enough solution to efiect the formation of a substantial amount of air pockets in the board, and then drying the board.

5. The process of impregnating fibre board with a salt consisting in impregnating said board by immersing it in a solution of a salt and then subjecting the solution with the board in it to a pressure less than atmospheric, then squeezing said board, after being removed from the solution, with sufficient pressure to reduce its volume enough to eifect the removal from within the board of enough solution to efiect the formation of a substantial amount of air pockets in the board, and then drying the board.

6. The process if impregnating fibre board with a salt consisting in impregnating said board by immersing it in a solution of a salt and then subjecting the solution with the board in it to a pressure greater than atmospheric, then squeezing said board, after being removed from the solution, with suflicient pressure to reduce its volume enough to effect the removal from within the board of enough solution to efl'ect the formation of air pockets in the board and then drying the board.

7. The process of impregnating fibre board with a salt consisting in impregnating said board by immersing it in a solution of a salt, then subjecting the solution with the board in it to a pressure other than atmospheric, then squeezing said board, after removing it from the solution, up to substantially its elastic limit for removing a substantial portion of said solution, and then drying the board.

8. The process of impregnating fibre board with a salt consisting in completely impregnating said board with a solution of a salt, then squeezing said board after being removed from the solution with suflicient pressure to reduce its volume enough to effect the removal from within the board of enough solution to effect the formation of air pockets in the board, and then drying the board. a

9. The process of fireproofing fibre board consisting in completely impregnating said board with a solution of di-ammonium phosphate, then squeezing said board, after being removed from the solution, with sufficient pressure to reduce its volume enough to effect the removal from within the board of enough solution to efiect the formation of air pockets in the board, and then drying the board.

ALEXANDER WINOGRADOW. 

